JP2000193538A - Capacitance-type inner force sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sensor low in height with satisfactory sensitivity by constituting a variable capacitance part out of a substrate in which one electrode is formed and an electrode plate arranged opposingly to the electrode to be elastically deformed by squeezing, providing a potential difference between both terminals of the variable capacitance part, and changing capacitance by squeezing operation. SOLUTION: An operating part S is formed of a circuit pattern DU, a substrate 1 in which electrodes Dx+, Dx-, Dy+, Dy-, and Dz are formed, a conductive metal plate 2 arranged on the substrate 1 opposingly with gaps to the electrodes Dx+, Dx-, Dy+, Dy-, and Dz, a decorative film 3, an operating button 4, and an adhesive double coated tape 5 as an adhesive and a spacer. In the operating part S, a variable capacitance part is formed of the metal plate 2 and the electrodes Dx+, Dx, Dy+, Dy, and Dz. Then, capacitance is changed when the sizes of gaps between the metal plate 2 and the electrodes Dx+, Dx-, Dy+, Dy-, and Dz are changed by the push of the operating button 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type force sensor.

[0002]

2. Description of the Related Art As a conventional force sensor of the capacitance type, for example, there is one as shown in FIG. This force sensor has electrodes Dx +, Dx-, Dy as shown in FIG.
A substrate 90 having +, Dy-, and Dz, an electrode plate D formed in a circular dish shape and arranged at a small interval from the substrate 90, and a stick erected at the center of the electrode plate 91. 91
And electrodes Dx +, Dx−, Dy +,
A voltage is applied to Dy- and Dz, and the electrode plate D is grounded. The sensor has an electronic circuit (block diagram) as shown in FIG. 12, and the capacitance between the electrode plate D and the electrodes Dx +, Dx-, Dy +, Dy-, Dz is defined as a voltage. You can output it.

[0003] Since this sensor has the above-described structure, the stick 91 is tilted in the X-axis direction.
As shown in FIG. 11, the gap between the electrode plate D and the electrode Dx + is reduced to increase the capacitance between them, and the gap between the electrode plate D and the electrode Dx− is increased to increase the static between them. The capacity decreases. The difference between the voltage V1 corresponding to the capacitance between the electrode plate D and the electrode Dx + and the voltage V2 corresponding to the capacitance between the electrode plate D and the electrode Dx− is determined by the electronic circuit. Amplified by
It is output as a voltage.

Therefore, by using this force sensor to make the direction of the operating force correspond to the moving direction of the cursor, and to make the magnitude of the operating force correspond to the moving speed of the cursor, for example, a pointing device of a computer Can be configured.

However, there is a problem that the force sensor cannot be made very thin due to the presence of the stick 91.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a capacitive force sensor having good sensitivity and low bulk.

[0007]

Means for Solving the Problems (Invention of Claim 1)
The capacitance-type force sensor according to the present invention comprises a substrate having at least one electrode formed thereon and an electrode plate which is elastically deformed by being pushed in and is arranged opposite to the electrode to constitute a variable capacitance portion. By providing a potential difference between both terminals of the variable capacitance unit and performing a pressing operation on the electrode plate, the capacitance of the variable capacitance unit is changed. (Invention of Claim 2) The capacitive force sensor according to the present invention is the same as the invention of claim 1, except that
Two electrodes provided at an interval of ° are formed, and these electrodes and an electrode plate constitute an X-axis variable capacitance unit. (Invention of Claim 3) The capacitive force sensor of the present invention is the same as the invention of claim 1, except that the substrate has a 90 ° angle.
Four electrodes provided at intervals are formed, and one opposing electrode and an electrode plate form a variable capacitance section of the X axis,
The Y-axis variable capacitance unit is constituted by the other opposing electrode and the electrode plate. (Invention of Claim 4) The capacitive force sensor of the present invention is the same as the invention of claim 3, except that a central electrode is provided on a substrate portion surrounded by four electrodes provided at 90 ° intervals. The central electrode and the electrode plate constitute a Z-axis variable capacitance section. (Invention according to claim 5) The capacitive force sensor according to the present invention is characterized in that, in the invention according to any one of claims 1 to 4, the electrode plate is a conductive metal plate or has elasticity. It is a plate-like body in which a conductive metal foil is formed on one side of a plate material having the same, or a conductive rubber plate. (Invention of Claim 6) In the capacitive force sensor according to the present invention, two time constant circuits are provided by combining a fixed resistor in each of the variable capacitance units on the X-axis. At the same time, the outputs from both time constant circuits are
C, and input a square-wave or sine-wave input clock whose phase is shifted to each time constant circuit, and the capacitance of the variable capacitance unit due to the pushing force on the electrode plate. The duty% of the output clock of the logic IC changes according to the change of the time constant of the time constant circuit accompanying the change. (Invention of claim 7) The capacitive force sensor of the present invention is the same as the invention of claim 3, except that the variable capacitance section of each axis is combined with a fixed resistor for each of the X and Y axes. It is assumed that two time constant circuits are provided, outputs from both time constant circuits are input to the logic IC, and further, a square wave or a sine wave input clock with a phase shift is input to each time constant circuit. The duty% of the output clock of the logic IC changes according to the change of the time constant of the time constant circuit accompanying the change of the capacitance of the variable capacitance section due to the pushing force on the electrode plate. (Embodiment 8) The capacitance type force sensor according to the present invention relates to the logic I according to the invention described in claim 6 or 7.
C is an exclusive OR circuit.

The function of the capacitive force sensor of the present invention will be described in detail in the following embodiments of the present invention.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1 and 2 show an operation section S of a capacitive force sensor, and FIG. 3 shows an electronic circuit K constituting the capacitive force sensor. Hereinafter, the operation unit S and the electronic circuit K will be described in detail. [Operation Unit S] As shown in FIGS. 1 and 2, the operation unit S includes a circuit pattern DU and electrodes Dx +, Dx-, and Dy.
+, Dy-, Dz, and electrodes Dx +,
Dx-, Dy +, Dy-, Dz, a conductive metal plate 2 disposed on a substrate 1 so as to face a gap with a gap.
(Corresponding to the electrode plate described in the section of means for solving the problem), a decorative film 3 covering the upper surface of the metal plate 2, and a low operation button 4 attached to the upper surface of the decorative film 3. And a double-sided tape 5 that adheres the circuit pattern DU and the corresponding metal plate 2 and functions as a spacer.

In this operation section S, the metal plate 2 and the electrodes Dx +, Dx-, Dy +, Dy-, Dz +
The variable capacitance units Cx +, Cx-, C shown in FIG.
When y +, Cy−, and Cz + are formed and no force acts on the operation unit S, from the mechanical symmetry, [the capacitance of the variable capacitance unit Cx +] = [variable capacitance unit Cx
−capacitance], [variable capacitance part Cy + capacitance]
= [The capacitance of the variable capacitance portion Cy-], [the capacitance of the variable capacitance portion Cz +] = [the capacitance of the fixed capacitance portion Cz-]. And metal plate 2
When the size of the gap between the electrodes Dx +, Dx-, Dy +, Dy-, and Dz + changes, the capacitance changes. [About the electronic circuit K that constitutes the capacitive force sensor]
As shown in FIG. 3, the electronic circuit K constituting the capacitive force sensor comprises an upper X-axis circuit K1, a middle Y-axis circuit K2, and a lower Z-axis circuit K3. I have.

As shown in FIG. 3, the X-axis circuit K1 includes variable capacitance units Cx + and Cx- respectively connected to fixed resistors R1 and Rx.
2 to form time constant circuits T1 and T2, and outputs from these time constant circuits T1 and T2 are EX-O
The input clocks CLI1 and CL of a square wave (or a sine wave) whose phases are shifted to the time constant circuits T1 and T2 are connected to the input section of the R logic IC [code IC1].
It is assumed that I2 has been input.

As shown in FIG. 3, the Y-axis circuit K2 includes variable resistance parts Cy + and Cy- each having fixed resistances R3 and R-.
4 in combination with time constant circuits T3 and T4, and outputs from these time constant circuits T3 and T4 are EX-O
The input clocks CLI1 and CL of a square wave (or a sine wave) whose phases are shifted to the time constant circuits T3 and T4 are connected to the input section of the R logic IC [code IC2].
It is assumed that I2 has been input.

As shown in FIG. 3, the Z-axis circuit K3 includes variable and fixed capacitance portions Cz + and Cz- each having a fixed resistance R
5 and R6 to form time constant circuits T5 and T6, and output from these time constant circuits T5 and T6 to E
It is connected to the input section of an X-OR logic IC [code IC3], and further has a square wave (or a sine wave) input clock CLI1, which is shifted in phase to each of the time constant circuits T5 and T6.
It is assumed that CLI2 has been input.

The resistance value of the fixed resistor is R1 = R
2, R3 = R4, R5 = R6, whereby
When no force is applied to the operation unit S, the time constants of the integration circuits connected to the input terminals of the circuits K1 to K3 are equalized (resistance and capacitance components generated in the circuit pattern are ignored). [Function of Capacitive Force Sensor] Now, as shown in FIG. 4, when the operation button 4 is pressed so as to reduce the gap between the electrodes of the variable capacitance portion Cx +, as shown in FIG.
(Gap between the electrodes of the variable capacitance unit Cx +) <(Gap between the electrodes of the variable capacitance unit Cx−).

In general, since capacitance = ε × (s / d) [ε: dielectric constant, s: electrode area, d: gap between electrodes] holds, (the capacitance of the variable capacitance portion Cx +)>
(The capacitance of the variable capacitance unit Cx−). In addition,
Although (the capacitance of the variable capacitance portion Cy +) and (the capacitance of the variable capacitance portion Cy−) also change, the changes become almost equal due to mechanical symmetry.

When the operation button 4 is pressed as shown in FIG. 5, the gap between the electrodes of the variable capacitance portion Cz + is reduced. In this case, the variable capacitance units Cx +, Cx−, Cy
The gap between the + and Cy- electrodes also becomes smaller,
The amount is smaller than that of the variable capacitance unit Cz +.

Here, the variable capacitance portions Cx +, Cx-, Cy +, Cy-, C by pressing the operation button 4 are pressed.
Table 1 summarizes the change in z +.

[0018]

[Table 1]

Though the operation is considered only in the direction in which the operation button 4 is pushed, if the operation button 4 is pulled in any way in the opposite direction, the change in the capacitance will be opposite to that shown in Table 1.

Considering the operation of the circuit of FIG. 3, the time chart is as shown in FIG. Input clock CLI2
Has a phase delayed by Δt from the input clock CLI1. Therefore, time constant R1 × (Cx +) = time constant R2 ×
(Cx-) but EX-OR logic IC [code IC
1] through (c) as shown in FIG.
Is output (when no load is applied).

Now, when the operation button 4 is pushed in as shown in FIG. 4, the capacitance of the variable capacitance portion Cx + changes greatly, and the time constant of the circuit becomes [(Cx +) + ΔC1] × R1>
[(Cx −) + ΔC2] × R2, and the voltage waveform (b) at the point B greatly changes like the voltage waveform (b ′). However, the voltage waveform (a) at the point A hardly changes and becomes a voltage waveform (a ′).

In the EX-OR logic IC [code IC1], the time width of the output pulse is Δt1, as shown in the output (c ′), corresponding to the change in the voltage waveform at the points A and B.
It increases by Δt2. These Δt1 and Δt2 correspond to the strength and direction in which the operation button 4 is pressed. This means that the EX-OR logic IC constituting the Y-axis circuit K2 [code IC
The same applies to the output of [2] and the output of the EX-OR logic IC [code IC3] constituting the Z-axis circuit K3.

Therefore, each EX-OR logic IC
From [codes IC1, IC2, IC3], the operation button 4
A pulse having a duty according to the direction and strength of pushing is output. This output pulse can be easily converted to an analog voltage by passing through a low-pass filter.

From the above, as shown in FIG. 7, if an appropriate processing circuit and a device driver of a computer are prepared, the device can be provided to a cursor coordinate control device for a computer. (Embodiment 2) In the capacitance type force sensor of Embodiment 2, as shown in FIG. 8, the portions corresponding to the decorative film 3 and the operation buttons 4 of the operation section S of Embodiment 1 are made of silicone rubber. The rubber member 6 is formed integrally with the metal plate 2 by using an adhesive 7. In the second embodiment, the operation unit S is sandwiched between the housing HU and the fixing unit F in the thickness direction.

The above-mentioned metal plate 2 can be replaced with metal foil or conductive rubber. (Embodiment 3) In the capacitive force sensor according to Embodiment 3, as shown in FIG. 9, an operation unit S is formed by mounting a metal plate 2 formed in an inverted dish shape on a circuit board DU formed on a substrate 1. To be stuck with a double-sided tape 5.

[0026]

Since the present invention has the above configuration, the following effects are obtained.

As is clear from the description in the section of the embodiment of the present invention, a capacitive force sensor having good sensitivity and low bulk can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an operation unit of a capacitive force sensor according to Embodiment 1 of the present invention.

FIG. 2 is a plan view of electrodes and circuit patterns formed on a substrate constituting the operation unit.

FIG. 3 is an explanatory diagram of an electronic circuit of the capacitive force sensor.

FIG. 4 is a sectional view showing a state in which an operation button of the operation unit is pressed.

FIG. 5 is a sectional view showing a state in which an operation button of the operation unit is pressed.

FIG. 6 is an explanatory diagram showing a relationship between an input clock, an output clock, and the like of the capacitance type sensor.

FIG. 7 is a block diagram when the capacitance type force sensor is used as a cursor coordinate control device for a computer.

FIG. 8 is a cross-sectional view of an operation unit of the capacitive force sensor according to Embodiment 2 of the present invention.

FIG. 9 is a cross-sectional view of an operation unit of a capacitive force sensor according to Embodiment 3 of the present invention.

FIG. 10 is a cross-sectional view of an operation unit of a capacitance type force sensor of the prior art.

FIG. 11 is a cross-sectional view when an operation unit of a capacitance type force sensor of the prior art is operated.

FIG. 12 is an explanatory diagram of an electronic circuit of a capacitive force sensor according to the related art.

[Explanation of symbols]

 1 substrate 2 metal plate Dx + electrode Dx- electrode Dy + electrode Dy- electrode Dz + electrode Cx + variable capacitance section Cx- variable capacitance section Cy + variable capacitance section Cy- variable capacitance section Cz + variable capacitance section Cz − Fixed capacitance

Claims (8)

[Claims] 1. A variable capacitance section comprising a substrate on which at least one electrode is formed, and an electrode plate which is elastically deformed by being pushed in and is arranged to face said electrode, and said variable capacitance section. Potential difference between both terminals of
A capacitance-type force sensor, wherein the capacitance of the variable capacitance section is changed by performing a pressing operation on the electrode plate. 2. An X-axis variable capacitance section is formed on a substrate by forming two electrodes provided at 180 ° intervals, and the electrodes and an electrode plate constitute an X-axis variable capacitance section. The capacitive force sensor according to claim 1. 3. The substrate is formed with four electrodes provided at 90 ° intervals, and the X-axis variable capacitance section is formed by one of the opposing electrodes and the electrode plate, and the other opposing electrode is formed. The capacitance type force sensor according to claim 1, wherein the Y-axis variable capacitance unit is constituted by the electrode plate and the Y-axis. 4. A central electrode is formed on a substrate portion surrounded by four electrodes provided at 90 ° intervals, and a Z-axis variable capacitance section is constituted by the central electrode and an electrode plate. The capacitance type force sensor according to claim 3, wherein the force sensor is provided. 5. The electrode plate is a conductive metal plate, a plate-like body having a conductive metal foil formed on one side of an elastic plate material, or a conductive rubber plate. The capacitive force sensor according to any one of claims 1 to 4, wherein: 6. A time constant circuit is provided by combining a fixed resistor in each of the variable capacitance units on the X-axis, and outputs from both time constant circuits are input to a logic IC. It is assumed that a square wave or sine wave input clock whose phase is shifted to the circuit is input, and the time constant of the time constant circuit changes due to the change in the capacitance of the variable capacitance part due to the pushing force on the electrode plate. Logic I
3. The capacitance type force sensor according to claim 2, wherein the duty% of the output clock of C is changed. 7. Two time constant circuits are provided by combining a fixed resistor with each variable capacitance section of each axis for each of the X and Y axes, and outputs from both time constant circuits are set to logic I.
C, and a square-wave or sine-wave input clock with a phase shifted to each time constant circuit. The capacitance of the variable capacitance unit due to the pushing force on the electrode plate is also assumed. 4. The capacitance type force sensor according to claim 3, wherein the duty% of the output clock of the logic IC changes in accordance with the change of the time constant of the time constant circuit accompanying the change. 8. The capacitive force sensor according to claim 6, wherein the logic IC is an exclusive OR circuit.